E.M.
My daugter is 11 months and we started solids at 7 months, too. She had MANY food sensitivties that sound a lot like your son's. She has done fine on solids. We based introducing them on the Joneja Allergen Scale, and I found this website SUPER helpful: http://www.wholesomebabyfood.com/allergy.htm
The scale is at the bottom of that page. Basically, we started at the bottom and are slowly working our way up.
I don't think teeth make much difference - my baby only has one tooth still and has only had it for a few weeks. But, she can EAT.
Solids at that age should be in addition to breastmilk, so just keep nursing as often as you do now and feed solids after nursing, not right before.
We steamed and mashed stuff like sweet potatoes and squash (both pretty hypoallergenic) and she did fine. Now that she's self-feeding, we cut stuff up into bite sized chunks for her.
I'm actually still on the elimination diet and will remain on it as long as she's breastfeeding, I think. We aren't introducing any allergens until after she's a year, for sure, and will do so slowly and in tiny amounts.
Good luck!!! Solids are fun!